1. Field
Exemplary embodiments of the present invention relate to a memory that may prevent degradation of stored data due to word line disturbance in a memory cell, and a memory system including the same.
2. Description of the Related Art
As the degree of integration of a memory increases, an interval between a plurality of word lines included in the memory is reduced. As the interval between the word lines is reduced, a coupling effect between adjacent word lines increases.
Whenever data is inputted and outputted to and from a memory cell, a word line toggles between an activated (active) state and a deactivated (inactive) state. In this regard, as the coupling effect between adjacent word lines increases as described above, a phenomenon occurs, in which a data of a memory cell connected to a word line adjacent to a frequently activated word line is damaged. Such a phenomenon is called word line disturbance. Due to the word line disturbance, a concern may be raised in that the data of a memory cell may be damaged before the memory cell is refreshed.
FIG. 1 is a diagram illustrating word line disturbance and illustrating a part of a cell array included in a memory.
In FIG. 1, ‘WLL’ indicates a word line having the large number of activation times, and ‘WLL−1’ and ‘WLL+1’ indicate word lines that are adjacent to the ‘WLL’, that is, word lines which are adjacent to the word line having the large number of activation times. Furthermore, ‘CL’ indicates a memory cell connected to the word line ‘WLL’, ‘CL−1’ indicates a memory cell connected to the word line ‘WLL−1’, and ‘CL+1’ indicates a memory cell connected to the word line ‘WLL+1’. The respective memory cells ‘CL’, ‘CL−1’ and ‘CL+1’ include cell transistors TL, TL−1 and TL+1 and cell capacitors CAPL, CAPL−1 and CAPL+1.
In FIG. 1, when the word line ‘WLL’ is activated or deactivated, the voltages of the word lines ‘WLL−1’ and ‘WLL+1’ are increased or decreased due to a coupling effect occurring among the word lines ‘WLL’, ‘WLL−1’ and ‘WLL+1’, and an influence is exerted on the amounts of charges of the cell capacitors CAPL−1 and CAPL+1. Therefore, frequent toggles of the word line ‘WLL’ between an activated state and a deactivated state lead to increased changes in the amounts of charges stored in the cell capacitors CAPL−1 and CAPL+1 included in the memory cells ‘CL−1’ and the ‘CL+1’, so that the data of the memory cells ‘CL−1’ and the ‘CL+1’ may be degraded.
Furthermore, as electromagnetic waves, which are generated while the word line toggles between the activated state and the deactivated state, introduce or discharge electrons into or from the cell capacitors of the memory cells connected to adjacent word lines, data may be damaged.